Advanced Text Editor with Ruler

        internal void InsertHyperlink(string text, string address, Color linkColor)
        {
            if (address == null) return; if (address == "") return;
            if (text == "") text = address;

            string _val = "", _val2 = "";
            string s = @"{\rtf1\ansi\ansicpg1251\deff0\deflang1049" +  //{\fonttbl{\f0\fnil\fcharset1200 Times New Roman;}}" +
                       Environment.NewLine + @"{\colortbl ;\red" + linkColor.R.ToString() + @"\green" + linkColor.G.ToString() + @"\blue" + linkColor.B.ToString() + ";}" +
                       Environment.NewLine + @"{\*\generator Msftedit 5.41.15.1507;}\viewkind4\uc1 ";
            string s1 = "\\pard  \\protect {\\field{\\*\\fldinst{HYPERLINK \"";
            string s2 = "\" }}{\\fldrslt{\\cf1\\ul ";
            string s3 = "}}}\\cf0\\ulnone\\f0 ";

            _val2 = "\\uc0 ";
            for (int i = 0; i < address.Length; i++)
            {
                _val2 += "\\u" + ((short)address[i]).ToString() + " ";
            }

            _val = s + s1 + _val2 + s2;

            _val2 = "\\uc0 ";
            for (int y = 0; y < text.Length; y++)
            {
                _val2 += "\\u" + ((short)text[y]).ToString() + " ";
            }

            _val += _val2 + s3 + Environment.NewLine + "\\protect0 " + Environment.NewLine + "}";

            this.SelectedRtf = _val;
        }

            if (m.Msg == 8270)
            {
                NativeMethods.ENLINK lParam;

                lParam = m.GetLParam(typeof(NativeMethods.ENLINK)) as NativeMethods.ENLINK;

                if (lParam != null)
                {
                    if (lParam.msg == 513)
                    {
                        string str = this.CharRangeToString(lParam.charrange);
                        if (!string.IsNullOrEmpty(str))
                        {
                            m.Result = (IntPtr)1;
                            OnLinkClicked(new LinkClickedEventArgs(str));
                        }
                        else base.WndProc(ref m);
                    }
                    else base.WndProc(ref m);
                }
                else base.WndProc(ref m);
            }

private class CharBuffer
        {
            // Fields
            internal char[] buffer;
            internal int offset;

            // Methods
            internal CharBuffer(int size)
            {
                if (size > 8196 || size < 0)
                {
                    this.buffer = new char[0];
                    return;
                }

                try
                {
                    this.buffer = new char[size];
                }
                catch (Exception)
                {
                }
            }

            public IntPtr AllocCoTaskMem()
            {
                if (this.buffer.Length == 0) return IntPtr.Zero;

                IntPtr destination = Marshal.AllocCoTaskMem(this.buffer.Length * 2);
                Marshal.Copy(this.buffer, 0, destination, this.buffer.Length);
                return destination;
            }

            public string GetString()
            {
                int offset = this.offset;
                while ((offset < this.buffer.Length) && (this.buffer[offset] != '\0'))
                {
                    offset++;
                }
                string str = new string(this.buffer, this.offset, offset - this.offset);
                if (offset < this.buffer.Length)
                {
                    offset++;
                }
                this.offset = offset;
                return str;
            }

            public void PutCoTaskMem(IntPtr ptr)
            {
                Marshal.Copy(ptr, this.buffer, 0, this.buffer.Length);
                this.offset = 0;
            }

            public void PutString(string s)
            {
                int count = Math.Min(s.Length, this.buffer.Length - this.offset);
                s.CopyTo(0, this.buffer, this.offset, count);
                this.offset += count;
                if (this.offset < this.buffer.Length)
                {
                    this.buffer[this.offset++] = '\0';
                }
            }
        }        
        private string CharRangeToString(NativeMethods.CHARRANGE c)
        {
            NativeMethods.TEXTRANGE lParam = new NativeMethods.TEXTRANGE();
            lParam.chrg = c;

            int size = (c.cpMax - c.cpMin) + 1;
            CharBuffer buffer = new CharBuffer(size);
            IntPtr ptr = buffer.AllocCoTaskMem();
            if (ptr == IntPtr.Zero)
            {
                return "";
            }
            lParam.lpstrText = ptr;
            int num1 = (int)NativeMethods.SendMessage(new HandleRef(this, this.Handle), 1099, 0, lParam);
            buffer.PutCoTaskMem(ptr);
            if (lParam.lpstrText != IntPtr.Zero)
            {
                Marshal.FreeCoTaskMem(ptr);
            }
            return buffer.GetString();
        }

this.TextEditor.SelectionOffsetType = ExtendedRichTextBox.OffsetType.Subscript;

this.TextEditor.SelectionCharOffset = -5;